Tropic
in astronomy, one of the two small circles of the celestial sphere, situated on each side of the equator, at a distance of 23° 28′, and parallel to it, which the sun just reaches at its greatest declination N. or S., and from which it turns again toward the equator, the N. circle being called the Tropic of Cancer, and S. the Tropic of Capricorn, from the names of the two signs at which they touch the ecliptic.
The stars are brighter in the tropics than in the temperate zones, and astronomical observation is easier. Cyclones arise within the tropics. The characteristic vegetation of the tropics consists of gigantic endogens, as palms, some of which rise to a height of from 100 to 200 feet. More polypetalous exogens are arborescent than in temperate climes. The Coniferæ exists chiefly on mountains. Ferns abound in tropical islands, and deltas where water is plentiful, so that in some localities from 250 to 300 species may be gathered.
The tropical type of vegetation was separated at a remote period into two portions, one in the Old World, the other in the New. Shells are brighter than in lands where the sun is less powerful, the birds more numerous and of gayer plumage, the feline tribe larger and in greater numbers.
In geography, one of the two parallels of terrestrial latitude corresponding to the celestial tropics, being at the same distance from the terrestrial equator as the celestial tropics are from the celestial equator. The one N. of the equator is called the Tropic of Cancer and that S. of the equator the Tropic of Capricorn. Over these circles the sun is vertical when his declination is greatest, and they include that portion of the globe called the torrid zone, a zone about 47° wide, having the equator for a central The regions lying between the Tropic of Cancer and the Tropic of Capricorn, or near them on either side, are called the tropics. line.